1. Field of the Invention
The invention relates to the grading of carcasses of animals such as large cattle, calves, hogs, or sheep.
2. Description of Related Developments
There are major differences in morphology and fat status of animals of a given species. Hence, after the animals have been slaughtered, the carcasses need to be graded to determine the price to be paid to the stock raiser and to determine the ultimate utilization, which is a function of the quality of each carcass.
This grading takes place at the end of the abattoir conveyors, namely after evisceration and preparation of the animals, on whole carcasses (calves, sheep) or half-carcasses (large cattle, hogs) suspended from a conveyor that advances continuously or stepwise.
In the case of large cattle, two independent criteria are used to grade the carcasses: conformation, and fat status. A European Community descriptive table based on visual assessment of these two criteria was officially published in the EC regulations of Apr. 28, 1981 and Oct. 12, 1981.
Conformation takes into account the quantity of meat on the carcass as a function of its dimensions. Conformation is determined by evaluating muscle shapes and thicknesses. Five grades have been defined, each characterized by one of the letters in the word EUROP. The conformation quality goes from grade E, which corresponds to a carcass of excellent conformation with convex profiles and excellent muscle development, down to grade P, which corresponds to a mediocre conformation with concave profiles and very meager muscle development.
Fat status is evaluated by examining the covering fat and the fat inside the rib cage. Five grades have been defined, each characterized by a number, from 1 for "very low" fat to 5 for "very high" fat.
Each conformation and fat status grade can be subdivided into three subgrades (+, =, -) to improve grading accuracy.
At the present time, the carcasses are graded by operators who inspect each carcass and assign to it a conformation grade or subgrade as well as a fat status grade or subgrade. It must however be borne in mind that this grading method, although it refers to an official table, is subjective in nature because it depends solely on visual assessment by an operator subject to varying work conditions. This brings about differences in the grading of a given carcass by different operators and in different abattoirs.
To overcome these disadvantages, the idea has been conceived of using devices that would provide a grading according to the EUROP European Community table that is less subjective and in particular more uniform over time and for different slaughter sites.
For this purpose, mechanical measuring methods have been devised. One solution, described in the Auge French patents No. 79 19310 and No. 80 17947, which is limited to evaluating the conformation grade, is unsatisfactory because each carcass to be graded has to be immobilized, made to contact a number of measuring elements, such as feelers, the measurements must be read, and finally the measuring elements must be removed, which may be troublesome at high speeds.
Devices also exist that measure fat status using a probe which must be driven into the tissues at particular points on the carcass and which give a measurement of the thickness of fat and muscle traversed by the probe. One such device is marketed under the tradename Fat-0-Meter and is made by SKF, Hennessy. Manual implementation is expensive and incompatible with high speeds. Automation is difficult because all carcasses are not the same size and are advancing along the conveyor.
Grading devices using video image analysis exist (Pfister SKG; Petersen, Danish patent application Ser. No. 6764/87), which yield a conformation grading by analyzing the contour of certain parts of the carcass and a fat grading by analyzing the contrast observed between fat and muscle. This device, studied on hogs, can provide an estimate of the meat yield but does not give satisfactory results for measuring the actual yield. In large cattle, whose carcasses are more complex than those of hogs, the device which is in the form of an enclosure containing a single video camera, does not produce grading according to the EUROP table sufficiently accurately and requires a manual probe to supplement the video measurements.